Willard question...

[dubob]

If I fillet fish out in the middle of the lake (leaving skin on for ID) is it legal to toss the carcasses back in?

In some cases, YES; in other cases, NO.

Possession of filleted fish
While you are in the act of fishing, it is unlawful to possess filleted fish from the current day’s catch or fish that have had their heads or tails removed. This does not apply to fish processed for immediate consumption or from a previous day’s catch. At most waters, you may fillet harvested game fish, or remove their heads or tails, after you have:
•Completed the act of fishing
•Arrived at camp
• Reached a fish-cleaning station
•Arrived at a principle means of land transportation
At Strawberry Reservoir, Scofield Reservoir, Lost Creek Reservoir and Panguitch Lake, you may not fillet trout and salmon, and you may not remove their heads or tails while in the field or in transit.
Note: Do not dispose of entrails and carcasses on the bank. Leave them in the water where you caught the fish.

At Willard, clean 'em out on the boat and dump the waste in the water.  I do.  Seagulls, crawdads, and catfish thank you for the extra vittles.